diff mbox series

[v3,4/6] folio: Add a function to get the host inode for a folio

Message ID 163584184628.4023316.9386282630968981869.stgit@warthog.procyon.org.uk (mailing list archive)
State New, archived
Headers show
Series netfs, 9p, afs, ceph: Support folios, at least partially | expand

Commit Message

David Howells Nov. 2, 2021, 8:30 a.m. UTC
Add a convenience function, folio_inode() that will get the host inode from
a folio's mapping.

Changes:
 ver #2:
  - Fix contradiction between doc and implementation by disallowing use
    with swap caches[1].

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/YST8OcVNy02Rivbm@casper.infradead.org/ [1]
Link: https://lore.kernel.org/r/162880453171.3369675.3704943108660112470.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/162981151155.1901565.7010079316994382707.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/163005744370.2472992.18324470937328925723.stgit@warthog.procyon.org.uk/ # v2
---

 include/linux/pagemap.h |   14 ++++++++++++++
 mm/page-writeback.c     |    2 +-
 2 files changed, 15 insertions(+), 1 deletion(-)

Comments

Matthew Wilcox Nov. 3, 2021, 1:16 p.m. UTC | #1
On Tue, Nov 02, 2021 at 08:30:46AM +0000, David Howells wrote:
> Add a convenience function, folio_inode() that will get the host inode from
> a folio's mapping.

I'm not opposed, but it only saves two characters, so I'm not entirely
sure it justifies its existance.  On the other hand, folio_inode() is
clear about what it does.

> + * For folios which are in the page cache, return the inode that is hosting
> + * this folio belongs to.

This looks like an editing mistake.  Either you meant
'return the inode that hosts this folio' or
'return the inode this folio belongs to'
(and i prefer the second).

With that grammo fixed,

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
David Howells Nov. 3, 2021, 2:34 p.m. UTC | #2
Matthew Wilcox <willy@infradead.org> wrote:

> > + * For folios which are in the page cache, return the inode that is hosting
> > + * this folio belongs to.
> 
> This looks like an editing mistake.  Either you meant
> 'return the inode that hosts this folio' or
> 'return the inode this folio belongs to'
> (and i prefer the second).

Yeah - I'll go with that.

David
diff mbox series

Patch

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 569302e4defe..fc4b7fcf4cc5 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -203,6 +203,20 @@  static inline struct address_space *page_mapping_file(struct page *page)
 	return folio_mapping(folio);
 }
 
+/**
+ * folio_inode - Get the host inode for this folio.
+ * @folio: The folio.
+ *
+ * For folios which are in the page cache, return the inode that is hosting
+ * this folio belongs to.
+ *
+ * Do not call this for folios which aren't in the page cache.
+ */
+static inline struct inode *folio_inode(struct folio *folio)
+{
+	return folio->mapping->host;
+}
+
 static inline bool page_cache_add_speculative(struct page *page, int count)
 {
 	VM_BUG_ON_PAGE(PageTail(page), page);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 9c64490171e0..c4d2414a92dd 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2960,7 +2960,7 @@  EXPORT_SYMBOL_GPL(folio_wait_writeback_killable);
  */
 void folio_wait_stable(struct folio *folio)
 {
-	if (folio->mapping->host->i_sb->s_iflags & SB_I_STABLE_WRITES)
+	if (folio_inode(folio)->i_sb->s_iflags & SB_I_STABLE_WRITES)
 		folio_wait_writeback(folio);
 }
 EXPORT_SYMBOL_GPL(folio_wait_stable);